CDS: what is driving positive basis

--market segmentation and idiosyncratic supply and demand factors e.g Tyco issued substantial amounts of convertible debt duinrg 2000 and 2001. Investors buy them becuse call options are cheap. At the same time, they buy CDS to shed credit risk, so CDS premium is high while ASW is low. --administractive and legal costs can be factored into CDS premium in practices.